Exploration of the dynamic equilibrium between the rare earth ion location within a RE-NaY zeolite and the FCC carbon deposition precursor

Abstract

In this research, a minute quantity of Ce was introduced into a NaY framework via the hydrothermal method, followed by gradient temperature calcination to acquire a series of Ce-NaY samples. Subsequently, a multi-dimensional characterization method was adopted. This method mainly included HRTEM analysis, XPRD structure refinement, Py-FTIR spectroscopy, in situ IR-catalytic conversion (using cyclohexene as the probe), and microreactor hydrogen transfer activity assessment. The aim was to precisely trace the location of the low-content Ce within the framework and uncover its regulatory mechanism for the “precursor” of FCC carbon deposition. The results indicated that the Ce_0.01-550Y sample achieved the lowest carbon deposition while maintaining the highest cyclohexane yield. Its excellent performance stemmed from the fine matching and synergistic effect of the Brønsted (B) acid and Lewis (L) acid densities. The findings demonstrate that the precise confinement of rare earth ions to designated sites within the SOD cages can effectively suppress the formation and evolution of carbon precursors (cyclohexene carbocation), thereby blocking the initiation pathway of carbon deposition and reducing its selectivity.